GRAPES-3
The GRAPES-3 experiment located at Ooty in India started as a collaboration of the Tata Institute of Fundamental Research, Mumbai, India and the Osaka City University, Osaka, Japan. At present many institutions from India and Japan are in collaboration.
GRAPES-3 is collaborative project between India and Japan. The Collaborating Institutes are:
GRAPES-3 (Gamma Ray Astronomy PeV EnergieS phase-3) is designed to study cosmic rays with an array of air shower detectors and a large area muon detector. It aims to probe acceleration of cosmic rays in the following four astrophysical settings. These include acceleration of particles to, (i) ~100 MeV in atmospheric electric fields through muons, (ii) ~10 GeV in Solar system through muons, (iii) ~1 PeV in our galaxy through nuclear composition of cosmic rays, (iv) ~100 EeV in nearby universe through measurement of diffuse γ-ray flux.
The GRAPES-3 is located at N11.4o, E76.7o, 2200m above mean sea level. The observations began with 217 plastic scintillators and a 560 m² area muon detector in 2000. The scintillators detect charged particles contained in extenstive air showers produced by interaction of high energy cosmic rays in the atmosphere. At present the array is operating with ~400 scintillators that are spread over an area of 25,000 m². The energy threshold of muon detectors is 1 GeV.
Objectives
Study of
- The origin, acceleration and propagation of >1014 eV cosmic rays in the galaxy and beyond.
- Existence of “Knee” in the energy spectrum of cosmic rays.
- Production and/or acceleration of highest energy (~1020 eV) cosmic rays in the universe.
- Astronomy of multi-TeV γ-rays from neutron stars and other compact object.
- Sun the closest astrophysical object, accelerator of energetic particles and its effects on the Earth.
Overview
The first cosmic ray experiment was started in 1955 by B.V. Sreekantan by setting up Cloud chambers that heralded the beginning of research at the Cosmic Ray Laboratory in Ooty. The next decade witnessed a variety of experiments involving high energy interactions and extensive air shower studies in this laboratory. World’s largest multiplate cloud chamber was operated here as part of an air shower array and significant results on the high energy nuclear interactions and cores of extensive air showers were obtained. Even before the advent of the first CERN accelerator of energy 30 GeV, a triple set-up comprising an Air Cerenkov Counter, a multiplate cloud chamber and a total absorption spectrometer was operated in the early seventies to study the differences in the characteristics of interactions with nuclei of protons and pions in the energy range 10-40 GeV. This enabled the time structure study of the nuclear active component of air showers and led to the discovery that the nucleon-anti-nucleon production cross-section considerably increases with energy.
In continuation of this high profile and pioneering work on cosmic ray research at CRL (Ooty), GRAPES-1 experiment was upgraded in various stages to GRAPES-2. However, due to the technical and administrative problem in its further expansion, a new experiment was set up at the RAC site 8 km from the old site which is called GRAPES-3. The GRAPES-3 experiment at present is operating with ~400 (each 1 m2) plastic scintillator detectors with a separation of 8 meters, to record the density and arrival time of particles in cosmic ray showers, and in conntinuous operation. At present, GRAPES-3 array is the highest density conventional EAS array in the world, and also, this experiment associated with a huge 560 m2 area tracking muon detector, is also the largest area tracking detector anywhere.
Members
Tata Institute of Fundamental Research, Mumbai, India
- S.K. Gupta
- K.P. Arun Babu
- S.R. Dugad
- B. Hari Haran
- I. Mazumdar
- P.K. Mohanty
- P.K. Nayak
- P. Jagadeesan
- A. Jain
- S.D. Morris
- B.S. Rao
- L.V. Reddy
Osaka City University, Osaka, Japan
- Y. Hayashi
- S. Kawakami
- S. Ogio
Aichi Institute of Technology, Toyota, Japan
- H. Kojima
J.C. Bose Institute, Kolkata, India
- S. Das
- S.K. Ghosh
- S. Raha
- P. Jordher
Indian Institute of Science & Engineering Research, Pune, India
- P. Subramanian
Indian Institute of Technology, Kanpur, India
- P. Jain
Chubu University, Kasugai, Aichi, Japan
- A. Oshima
- S. Shibata
Hiroshima City University, Hiroshima, Japan
- K. Tanaka
Kochi University, Kochi, Japan
- T. Nakamura
Aligarh Muslim University, Aligarh, India
- S. Ahmed
North Bengal University, Siliguri, India
- A. Bhadra
- R.K. Dey
Vishwakarma Institute of Information Technology, Pune, India
- C.S. Garde
Interesting Results
Several fascinating results have recently been obtained from the GRAPES-3 experiment on a variety of topics, a few of which are listed below.
- Measurement of primary composition in the energy 50 TeV - 1 PeV overlapping with direct measurements
- Precision measurements of Forbush decrease events including rigidity dependence of its amplitude
- Measurement of turbulent magnetic field in the shock-sheath region in the Coronal mass ejections (CMEs) by using multi-rigidity muon data
- Precision measurement of the solar diurnal anisotropy and its higher harmonics including its rigidity dependence
- Precision measurement of the density gradient of cosmic rays in the solar system by probing Swinson flow
- Precision measurement of the anti-correlation between changes in solar wind velocity and cosmic ray intensity
R&D on detectors and electronics
The Cosmic Ray Laboratory has been at the forefront for the development of state-of-the-art detectors and electronic instruments in an effort to produce and use world-class equipment a few of which are also mentioned below. Most of the equipment costs ~10% of imported equipment, maintenance is inexpensive and prompt because of the in-house expertise, equipment can be optimized depending on the specific requirement of the experiment.
- High quality fast plastic scintillators (first time in India) with long attenuation length and high photon output
- Ultra-fast amplifiers amd discriminators with time jitter ~100 ps
- Time to digital converters (TDCs)
- General purpose boards with USB and TCP/IP interface
- FPGA boards for triggering and for data acquisition purposes
Journal Publications
- Transient Weakening of Earth’s Magnetic Shield Probed by a Cosmic Ray Burst. P.K. Mohanty, K.P. Arunbabu, T. Aziz, S.R. Dugad, S.K. Gupta, B. Hariharan, Y. Hayashi, P. Jagadeesan, A. Jain, S. Kawakami,H. Kojima, S.D. Morris, A. Oshima, B.S. Rao, S. Shibata, S. Raha, P. Subramanian https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.117.171101